Documentation

There are two very different things one might want to do with Augeas:

use its public API and existing file format descriptions to edit config
files

write new file format descriptions

Using the Augeas API

If you are mainly interested in Augeas' public API, the best documentation
right now is the public header file augeas.h and augtool's
help command. The commands in augtool mirror the public API
closely, and therefore give you an easy way to tinker with it without
writing any code.

Writing schemas

If you are mainly interested in describing new file formats, you should
read about lenses, the basic building blocks of the transformation
between files and the tree, and the tutorial on writing schemas.